hterm: fix tests after default encoding change
hterm: fix tests after default encoding change

Some of these tests use graphic character maps, so make sure we set
the encoding back to iso-2022 regardless of the default (which we
have changed to utf-8).

BUG=chromium:747625

Change-Id: I93812dcfe29c918819f3edbd6bcd5a1b25b608ec
Reviewed-on: https://chromium-review.googlesource.com/789437
Reviewed-by: Brandon Gilmore <adbfbaf7e4f927b45ce8ad3e5043a632414a833b@google.com>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

chromium/hterm,chromium/hterm,chromium/hterm,chromium/hterm